add docker-image build and push pipeline

.github/workflows/docker-image.yml

@@ -0,0 +1,38 @@
+name: Docker Build and Push
+
+on:
+  push:
+    branches:
+      - main
+
+jobs:
+  build_and_push:
+    name: Build and Push
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out the repo
+        uses: actions/checkout@v3
+
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v2
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v2
+
+      - name: Login to GitHub Container Registry
+        uses: docker/login-action@v2
+        with:
+          registry: ghcr.io
+          username: ${{ github.repository_owner }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Build and push
+        id: docker_build
+        uses: docker/build-push-action@v4
+        with:
+          context: .
+          push: true
+          tags: ghcr.io/${{ github.repository_owner }}/nostr-rs-relay:latest
+
+      - name: Image digest
+        run: echo ${{ steps.docker_build.outputs.digest }}